Carb vs. EFI cam

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ValiantOne

ValiantOne

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Hey all,

I am planning my magnum swap and had a question about cams for carb vs. efi motors. I was thinking about going carb to start and eventually switch to efi. I noticed that the LSA is different on the cams for these applications. Why the difference? Would a cam for one application severly hamper power in the other application?

Thanks

CE
 
I got a 100k mile early 90's Magnum 360 & stuck a performer intake, edelbrock 650 with some hooker headers, tremec 5 speed & it ran awesome. Stayed with the stock cam in it. It would outrun lightly modified LS F-bodies(zo6 intake/cam/headers).

I don't think you'll have any issues.
 
I´m no expert, as far as i understand EFI could have trouble with low vacuum signal. So you should possibly stay away from cams with low LSA like 104 - 108° when using EFI, because due to the bigger overlap with given duration these cams will have less vacuum signal compared to, let´s say a cam with 112° LSA.

Michael
 
ValiantOne said:
Hey all,

I am planning my magnum swap and had a question about cams for carb vs. efi motors. I was thinking about going carb to start and eventually switch to efi. I noticed that the LSA is different on the cams for these applications. Why the difference? Would a cam for one application severly hamper power in the other application?

Thanks

CE
Click to expand...

I run the Factory JTEC EFI with a Hotwire Hotrod harness and an SCT Tuned ECM out of a non-security fob'd manual trans 3/4 tone Dodge Ram.

I was running a mild 110* LSA cam in both my stock stroke stock head 5.9 Magnum and my 408" stroked Eddie headed Magnum. I've since swapped in a 108* LSA cam with slightly more duration and lift in the 408" motor.

The 108* LSA cam really woke up the motor in the midrange and top end. It helped it take advantage of the Hughes Supper Prepped heads with additional hand blending in the ports. This motor has a bit higher compression too, and cranks 200 psi.

I haven't measured the vacuum at idle, but the tuner compensated for this with the tune. Hughes states this combo should crank out 510+ hp with this cam. The way it runs, I believe its in that range.

Cam selection is really about getting ALL the driveline components matched to work together from gear ratios, trans stall, induction, heads, compression and exhaust. What works in one combo could be less effective in most others.

It also has to hook up. My '68 is most effective when it's coming out of the hole, but does pretty decent all the way down the track.
 
Jcb426, I spoke to James at Hughes today. He echoed what you said basically. He told me that the narrower lsa could be accounted for in the programming when I went efi with it. Cool.

Now the question is what cam, but that is another thread...... I'm going to get all my spec's together and intended use, etc. and do a different thread on that.
 
ValiantOne said:
Hey all,

I am planning my magnum swap and had a question about cams for carb vs. efi motors. I was thinking about going carb to start and eventually switch to efi. I noticed that the LSA is different on the cams for these applications. Why the difference? Would a cam for one application severly hamper power in the other application?
Click to expand...

The issue is only with "no laptop, hands off, self tuning" systems such as the FAST EZ, FITECH, ectera, and only at idle. That's because they use engine vacuum as a measure of load and they try to self adjust at idle where camshaft reversion with low LSA cams confuses the algorithm. This is NOT a problem with any EFI system where you can turn off the self tuning at idle and set that yourself. Obviously EFI works great with race motors and they have camshaft reversion in spades.
 
360duster said:
I´m no expert, as far as i understand EFI could have trouble with low vacuum signal. So you should possibly stay away from cams with low LSA like 104 - 108° when using EFI, because due to the bigger overlap with given duration these cams will have less vacuum signal compared to, let´s say a cam with 112° LSA.

Michael
Click to expand...
So how are they acting when having a "wrong" cam w/ self learning f.i. ?
 
360duster said:
I´m no expert, as far as i understand EFI could have trouble with low vacuum signal. So you should possibly stay away from cams with low LSA like 104 - 108° when using EFI, because due to the bigger overlap with given duration these cams will have less vacuum signal compared to, let´s say a cam with 112° LSA.

Michael
Click to expand...
THIS IS TRUE, experiencing it right now myself!
 
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